Hydraulic Efficiency of Grate and Curb Inlets - Urban Drainage and ...

• The inlet efficiency appears to asymptotically approach a minimum value as the
velocity increases.
• As the inlet length increases for a given flow velocity, the efficiency increases.
• The spread of water across the street section for a given flow decreases as either of
the slopes increase.
• For a given longitudinal slope, a lower cross slope shows a slightly faster rate of
decrease in efficiency as the velocity increases.
• For a given cross slope, a lower longitudinal slope shows a slightly faster rate of
decrease in efficiency as the velocity increases.
• For a given inlet length, the Type 16 inlet is generally the most efficient, followed by
the Type 13 and Type R.
4.2 Sump Tests
A tabular sample of the sump test data is presented as Table 4-2. All of the flow into the
model was captured by the inlets in the sump test condition. The entire sump test data set is
included as Appendix C.
Test ID
Number
Configuration
Table 4-2: Sample sump test data
Longitudinal
Slope
(%)
Cross
Slope
(%)
Flow
Depth
(ft)
Prototype
Flow
(cfs)
1 Triple No. 13 0 1 0.333 2.5
2 Triple No. 13 0 1 0.501 8.6
3 Triple No. 13 0 1 0.999 42.2
4 Double No. 13 0 1 0.333 2.3
5 Double No. 13 0 1 0.501 7.8
6 Double No. 13 0 1 0.999 27.1
7 Single No. 13 0 1 0.333 2.0
8 Single No. 13 0 1 0.501 5.9
9 Single No. 13 0 1 0.999 15.3
The sump test data are plotted in Figure 4-4 through Figure 4-6 for increasing flow depth
for the three inlets tested.
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